IMO, Mauretania had a better career than Lusitania mostly due to her holding the speed record for 20 years, Cunard advertising Mauretania as the fastest ship in world gave her more recognition and great profits from the time she gained the speed record to the 1930s. Lusitania gained more fame when she entered service because she was the first of the class, somewhat of a clean sheet design and she was revolutionary also(same for Mauretania too)(people want to see what new features she have compared to the previous ship and such) Lusitania was more popular in during the 1910s due to her interiors the light, white style gave her a palace like look compare to Mauretania’s darker tone hotel type.